402 Chevy LS2 Short Block Engine Build - Thumper

Easily Made Eight With A 402ci LS2

It's a little intimidating at first. You know it's just another engine. It's got all the same stuff a traditional small-block has, like pistons, crank, rods, a cam, and lifters-but this one has been masked in an unfamiliar dress. This one is skinned in aluminum and lacks the traditional painted iron block and deep-sumped oil pan. Plus it sports metric hardware instead of the American units we are accustomed to. Don't kid yourself though. This all-aluminum mill means business, and it has become one of GM's tried-and-true thoroughbreds of the new millennium.

For this month's test, rather than piecing something together from scratch, we opted for a complete LS2 short-block from Turn Key Engine Supply out of Oceanside, California. Inside the aluminum fortress rests a Lunati LS1 Pro Series stroker kit assembly featuring a 4340 forged crankshaft with a 4.00-inch stroke, 4340E billet rods, and forged JE Pistons with valve reliefs.

Once we began to unzip its skin to reach the insides, it was clear GM knew what it was doing from the factory. Cam swaps from stock to aftermarket can be achieved without dropping the oil pan. Case in point, we had two solid-rollers to try out. The first was right out of Comp's catalog (PN54-500-11), which specs out at 235/240 intake/exhaust and 0.646/0.641 intake/exhaust duration at 0.050 inch with 113 lobe separation, while our second, more aggressive cam (PN 54-501-11) features a 243/248 intake/exhaust and 0.653/0.648 intake/exhaust duration at 0.050 with 113 lobe separation. Both were paired with a set of their linked solid-roller lifters. Our cylinder heads of choice? We couldn't pass up a chance to test Trick Flow's newest fully CNC'd units. They feature 340 cfm of flow at 0.600-inch lift. Additionally, the build wouldn't be complete without throwing a little juice and fuel down the mouth of an Edelbrock Victor Jr. manifold via a Holley 1,000-cfm HP carburetor and a Zex perimeter plate.

How well did our 402-inch short-block fare with the new cams, lifters, and tremendous flow from the cylinder heads? Read on. We think you'll be impressed by the results.

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402 Chevy LS2 Short Block Engine Build - Thumper

Since we were starting with Turn Key's 402-inch short-block, the only components removed to gain access to the cam were the balancer and front timing cover. We used an 8mm socket to remove the cover bolts, and once it was out we found TDC and pulled the cam.

To find TDC, Ernie Mena lined up the timing dots on the upper and lower gears. Once they were matched up, we could remove the timing gear bolts. The cool part about this: The oil pump doesn't need to be removed and neither does the lower crank gear.

With the timing gear off and the chain off to the side, we removed the Torrington bearing and cam plate.

We wanted to take full advantage of the LS2's high revving potential with the new solid-roller camshaft, and that meant the hydraulic lifters had to take a hike. In order to access the lifters, we first removed the factory lifter tray and simply pulled them out.

With the lifters out, we could then remove the old camshaft, all the while being careful not to nick the cam bearings. When installing the new camshaft, be sure to place liberal amounts of assembly lube on the cam lobes before sliding it in.

For head gaskets we went with Fel-Pro MLS (PN 1161R and PN 1161L), which have a 4.100 bore and a compressed thickness of 0.053 inch. The multilayer design can withstand higher combustion chamber pressures, which we were anticipating with the added use of nitrous. To prevent any confusion over which way the head gaskets should lie, each gasket is labeled either "L" for the driver side or "R" for the passenger side.

Once our 'stick was in, we dropped in our new solid-roller lifters (PN 8956-16) with the links facing toward the lifter valley. Next, we began to button up the front of the engine by reinstalling the cam plate and making sure to line up the timing marks. From there, we placed the cam gear back on with the chain, and that's it.

Lift OffWe opted for Comp's new solid-roller lifters for our LS2 mill. This new design delivers a weight savings of 14 grams per tappet over the earlier 8950 Gen III solid-roller tappets, which will help the LS2 to rev even higher, thanks in part to the reduced valvetrain weight. Additional features include an enhanced pressure-fed oiling design, including EDM Oil Injection to the roller axle and bearing, a tool steel axle, and precision-sized needle bearing rollers-and our favorite part is that these are rebuildable.

For added clamping force, we utilized ARP's cylinder head stud kit (PN 234-4317). To install them, we applied moly on both the upper and lower threads, drove them into the block, and snugged them up with an Allen wrench.

Our Trick Flow heads and Fel-Pro gaskets required a three-step torquing method. We began the torquing at 50 ft-lb, went up to 70, and finished at 85. For the smaller studs that run along the top of the heads, we torqued those to 25 ft-lb.

We then installed the rocker studs into the heads, but first placed thread-sealer on the eight studs that actually enter the intake port through the head. Once all 16 studs were threaded, we torqued each one with its guideplate to 30 ft-lb.

Flow For GoTrick Flow's latest CNC-designed 235cc cylinder heads mean business. Priced at $2,500 for a complete off-the-shelf set, they include 70cc combustion chambers (64cc and 65cc configurations are also available with a 220cc port) 2.08/1.60 intake/exhaust valves, springs, and locks and retainers, and they're ready to run. Check out these massive flow numbers.

Lift Value

Intake CFM

Exhaust CFM

0.100

65

55

0.200

144

124

0.300

229

196

0.400

287

242

0.500

323

260

0.600

340

270

Before dropping in the Comp Cam's 8.22-inch-long, 5/16-inch Hi-Tech pushrods, we ran them through solvent and blew them dry to prevent any potential clogging. Next, we coated each end with high-pressure lube to prevent dry-start.

Up top we forged on with a carbureted Edelbrock Victor Jr. manifold with a Holley 950-cfm HP carb. There's no need to mess with gaskets here. Instead, this manifold integrates the factory Neoprene gaskets into each port.

We couldn't hack seeing the stock LS2 valve covers on this mill. We ended up scouring the Net for something a little more aesthetically pleasing. The answer came in the form of Moroso's fabricated aluminum pieces. If you pick up a set for yourself, know that they still use the main factory bolts and gaskets. We also installed Moroso's trick coil-pack mounting brackets and complete wire set. These slick brackets are anodized and feature a hinge to gain access to the valve cover bolts underneath. This is our first experience with these units, and we don't see us going back to the factory pieces-ever.

In typical CHP fashion we left no options unturned in search of additional horsepower. We used a Holley 950-cfm HP for our baseline pulls and made 589 hp and 534 lb-ft. As testing progressed, we stepped up the cfm and fuel demands by using a Holley 1,000-cfm HP and added a 1-inch Wilson spacer, which then bumped power to 608 hp and 542 lb-ft. However, for all the beans, we topped it off with a Zex perimeter plate. Being conservative, we tested the waters with a 150 shot and produced 744 hp and 763 lb-ft. We didn't stop there. Stepping up to a 200 shot rang the bell with 780 hp and 801 lb-ft!

Check out this 383 Short Block Engine build for under 10 grand and see how we get over 450 horsepower. Only at www.chevyhiperformance.com, the official site for Chevy High Performance Magazine. » Read More